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An Icelandic volcano brought much of the world's air travel to a halt. And then it brought the world to Iceland.

Few outside this island nation had heard of Eyjafjallajokull - and even fewer could pronounce it - when the volcano erupted in April 2010 after two centuries of silence, spewing an ash cloud that closed Europe's airspace and grounded millions of travellers.

Iceland responded to its global notoriety with savvy self-promotion, sparking a tourism boom to a country whose landscape of hardened lava, gushing geysers and steaming hot springs has a stark beauty that's like nowhere else on Earth.

So the prospect of a new eruption brings a mix of trepidation and anticipation.

"We are kind of waiting for it," said Thordis Olafsdottir, who runs the tourist office in Vik, a village at the base of Katla, a volcano that recently began rumbling after decades of quiet.

"It has been almost 100 years since it erupted," she said. "It is ready."

Like many Icelanders, Olafsdottir has a matter-of-fact attitude to life on this unpredictable island, whose hazards include earthquakes, volcanic eruptions, avalanches and floods, as well as volatile North Atlantic weather that can bring rain, sleet, hail, snow and sunshine in one day.

Iceland is home to 32 active volcanic sites, and its history is punctuated with eruptions, some of them catastrophic. The 1783 eruption of Laki spewed a toxic cloud over Europe, killing tens of thousands of people and sparking famine when crops failed. Some historians cite it as a contributing factor to the French Revolution.

Most other volcanoes remained largely a local threat - until Eyjafjallajokull blew its top in April 2010. Aviation authorities closed much of European airspace for five days out of fears volcanic ash could damage jet engines, and the phones at Iceland's Department of Civil Protection started ringing off the hook.

"News agencies that we didn't even know existed - countries we didn't know existed - were calling us," said the department's Detective Chief Inspector Rognvaldur Olafsson. "We were even getting phone calls from the public, and emails: 'You have to do something about this volcano. Can you make it stop?"'

Iceland was briefly infamous as the country that stopped the world. But tourism authorities responded with a clever advertising campaign, creating TV and online ads in which Icelanders and visitors described how they were "Inspired by Iceland." News footage of lava-spewing craters helped make the country look cool and beautiful, with a hint of danger.

Suddenly, Iceland was hot. Some 1.8 million people - almost six times the country's population - are expected to visit this year, up from half a million in 2010. They are an economic godsend to a country still scarred by the 2008 financial crisis, which collapsed Iceland's banks and sent unemployment soaring.

Katla has helped turn sleepy Vik, a community of 300 people some 180km east of the capital, Reykjavik, into a tourism hot spot. On a busy day it attracts hundreds of visitors who come to see the stark black sand beach, where jagged columns of basalt rock rise from the sea, and to hike up the Myrdalsjokull glacier, under which the volcano lies, invisible but rumbling.

Katla is one of Iceland's largest and most feared volcanoes. Its last eruption, in 1918, lasted almost a month, unleashed floodwaters the size of the Amazon and extended Iceland's coast by 5km.

Passengers delayed by the eruption wait for updates at Auckland International Airport. Photo / NZ Herald

Like about half of Iceland's volcanoes, it lies under glacial ice hundreds of metres thick. Eruptions melt the icecap, unleashing floodwaters that can destroy roads, buildings and powerlines, and send icebergs the size of houses hurtling downhill. There are also risks from ash, lava and poisonous gases spewed by the volcano.

But Vik is eager for volcano-related opportunities. Olafsdottir says eruptions are an annoyance and a danger, but "after, it's great."

Visitors flock to see still-warm lava and newly created craters. The eruption of the Bardarbunga volcano in 2014 even created a new tourist attraction - a natural hot tub where warm lava meets glacier water.

But Iceland's volcanoes remain potentially lethal. Since Eyjafjallajokull, Iceland has improved its already well-developed system of volcano monitoring, warning and emergency response.

At the Icelandic Meteorological Office in Reykjavik, meteorologists, seismologists and volcanologists watch hundreds of sensors that monitor seismic activity, signs of volcanic inflation and gas emissions - evidence that magma from deep underground is being pushed to the surface.

Still, said Sigrun Karlsdottir, the Met Office director of natural hazards: "It is almost impossible to say when the next eruption will take place."

The biggest earthquakes in decades rattled Katla in late September, prompting authorities to raise their alert level and ramp up emergency procedures. The earthquakes subsided, but scientists say Katla usually erupts twice a century and is long overdue.

When it blows, residents in Vik may have only 15 minutes before they are enveloped in pitch black ash. Locals are well rehearsed in what to do - head to the church perched on a hill, the highest spot in town.

Authorities are developing new ways of making sure visitors know it, too. Police can send text messages to everyone in an affected area, and also issue safety warnings through television, radio, websites and social media.

"Trying to get that information across has always been a challenge, but it's more of a challenge now because we have so much more of tourism than we used to have," said Olafsson.

He says tourists are most welcome in Iceland, even if they have a tendency to do silly things, like go hiking in the mountains wearing sneakers and a T-shirt or climb a volcano without taking precautions.

Like almost everyone in Iceland, Olafsson wants tourists to see his country as safe and welcoming - but to stay alert.

"If you were going to be worried about anything that might happen you'd probably be best staying at home," he said.

"You have to respect nature when you come to Iceland, and you have to be aware of where you are and what can happen."